Stomach-action molluscicides

ABSTRACT

A stomach-action molluscicide including a metal complexone as an active ingredient. The term &#34;complexone&#34; as used herein refers to an organic ligand containing at least one iminodiacetic group --N(CH 2  CO 2  H 2 ) 2  or two aminoacetic groups --NHCH 2  CO 2  H which form stable complexes with most cations. Preferably, the complexone is a derivative of ethylenediaminetetraacetic acid.

FIELD OF THE INVENTION

The present invention relates to stomach-action molluscicides, stomachpoisons or edible baits containing them and their use in killing,controlling and/or inactivating molluscs, in particular, slugs andsnails.

BACKGROUND TO THE INVENTION

Slugs and snails are major pests of agriculture in many parts of theworld. Their biology tends to favour activity in moist conditions suchas habitats which are continually wet and temperate regions, especiallyduring rainy summers and autumns. As a consequence, their potential fordamage is considerable.

The-ecologies of different types of molluscs, which can be eitherterrestrial or aquatic, are very different and they usually requiredifferent types of treatment. The snail species Theba pisana, Cernuellavirgata, Helix aspersa and Achatina spp and the slug species, Arionhortensis, Milax budapestensis, Deroceras reticulatum and Limax maximusare of particular interest as targets. The common garden snail, Helixaspersa, and the grey field slug, Deroceras reticulatutni, are commongarden pests throughout temperate Australia. These pests haveestablished themselves in many parts of the world, adapting to a widerange of climatic conditions. They rarely increase in numbers above 20per square meter but cause darnage by feeding, with minor damage due tothe mucus on which they move. Helix aspersa is, in general, a nocturnalfeeder and in the daytime remains hidden on the underside of leaves,under rocks or in cracks in the soil. It flourishes in moist conditions.On the other hand, there are a group of snails which have beenintroduced into Australia in the twentieth century. The areas in whichthese are pests (often over 200 per square meter) are still expanding.These are the white Italian snail, Theba pisana and the vineyard orMediterranean snail, Cernuella virgata, which can survive long hotsummer temperatures by aestivating on weeds and fence posts, retreatinginto their shells and secreting a hard mucous film to reduce moistureloss and rest. These snails are of some concern to Australian farmersbecause they also aestivate on the heads of cereal stalks in Novemberand December and during harvest, they clog up the machinery andcontaminate the grain, making it either unacceptable or forcing it to bedowngraded. There are very significant variations of the pest numbersand in a bad year it is uneconomic to harvest substantial areas ofcrops. In cold climates, Theba pisana hibernates in winter. The slug,Deroceras reticlilatum, is found throughout temperate areas of the worldand it is the major slug variety found in both Australia and the UnitedKingdom.

Significant crop damage by molluscs also occurs in northern Europe, theMiddle East, North and Central America. South East Asia, Japan and NewZealand. In many cases, the rise to pest status of the slug or snail inquestion is a consequence of change--either in distribution (as in thecase of accidental or deliberate introductions) or in agriculturalpractice, where new crops or systems of cultivation may enablepopulations to rise to pest levels. For example, approximatelytwo-thirds of the molluscicides in the United Kingdom are used on winterwheat and winter barley. After harvesting, there is a significant amountof stubble left behind. It is present agricultural practice to drillseeds of the next crop directly into the soil, without removing thestubble of the previous crop by, for example, burning. Slugs, which haveburied themselves in the soil, move along into these drill holes and eatthe inside out of the new seed, thereby potentially destroying the wholeplanting. Slugs are therefore a major agricultural pest.

Devising methods of controlling these pests presents a formidable task.Control methods involve cultivation practices, chemical and biologicalmethods. Cultivation procedures that remove or make the habitat of themollusc less attractive, are usually less expensive. Biological controlby introduction of natural predators is a preferred method because, inprinciple the predator could be snail specific and not harm nativesnails or non-target organisms. However, very extensive testing isrequired and, once predators have been introduced, it is very difficultto reverse the process and to remove them. Chemical methods(molluscicides) involve the use of a contact or stomach poison, anirritant or a feeding depressant.

The environment which the mollusc inhabits is generally treated with themolluscicide which is then ingested by the mollusc. Since most snailsand slugs thrive in moist conditions, any effective molluscicide shouldbe effective under these conditions. This feature of appropriate waterresistance has major implications in broad-acre agriculture, where onetreatment is preferred rather than multiple applications throughout thecrop season. In this case, it is desirable to have a balance betweenwater resistance and efficacy to prevent the pellets functioning aspoisons after the crop has been harvested and livestock has moved intothe area to feed. In addition, in areas of very high moisture contentthere should be effective water-proofing to ensure the poison ismaintained in an ingestable form for a sufficient time to permitadequate exposure to the molluscs. Since moisture is essential for slugand snail activity, damage is likely to be more severe on heavy soilsdue to their greater moisture retention. However, damage is notrestricted to heavy soils. Slug and snail activity is encouraged by highlevels of organic matter which often provides a moist environment.

Green manure crops and old crop residues used in the compost heap oftenallow populations to build up quickly. Dense leafy plants, such asbrassica and curcubitis, provide a moist humid canopy under which snailsand slugs thrive. Temperature also affects the level of slug and snailactivity. Indeed, this activity peaks around 15-20° C. and decreasesmarkedly below 5° C. and above 30° C. Furthermore, low temperaturessignificantly delay the hatching of slug eggs. Most slug and snailspecies are nocturnal feeders. Hence, watering of gardens in the eveningoften provides an environment which encourages increased feedingactivity.

Molluscicides for use against slugs and snails can be divided into threegroups. These are contact-action molluscicides, such as aluminum andcopper sulfate crystals, which are applied to the area inhabited by thesnail or slug and are taken up passively when the snail or slug moves inthis area; irritant powder molluscicides, such as silica grains, whichact by being taken up in the snail's or slug's locomotion mucus; andstomach-action molluscicides such as metaldehyde and methiocarb pellets,which are ingested by the mollusc.

Contact-action molluscicides are generally applied in the form of spraysand dusts to crops and the mollusc receives a fatal dose of toxin bymoving over the crop. Molluscs present problems of delivery of the toxinbecause their relatively large size means that a large dose of toxin isnecessary. They are also relatively immobile and may remain concealed incomparative safety for long periods. These problems are furthercomplicated by the layer of mucus which invests molluscs. Irritantmaterials stimulate mucous production and can be sloughed off and leftbehind in a discarded mucous coat. As the mucus is largely composed ofwater, the water-solubility of candidate contact poisons is therefore aprerequisite if they are to be able to penetrate the mucous barrier.However, hydropthilic properties in a toxin also increase the rate atwhich it is diluted by rain and leached into the soil.

Delivery of effective amounts of bait is also a problem. A sufficientamount of poison must be ingested to ensure a lethal dose. In general,most toxic compounds are also repellent and the interaction of toxicitywith repellency prevents the ingestion of sufficient poison to kill themollusc. There are three major effects of molluscs ingesting poisonbaits. Firstly, there is a possible repellency away from the crop by thebait. Secondly, ingestion of the bait may cause reduced feeding andthirdly, the poison may kill the snail or slug involved.

Until the mid 1960's, the most effective molluscicide was metaldehydewhich is a tetramer of acetaldehyde. In Europe, it was known only as asolid fuel, until its molluscicidal properties were discoveredaccidentally in France by farmers who found dead and dying snails on andaround metaldehyde tablets discarded after use in camping stoves.Metaldehyde is toxic at high concentrations and an irritant at lowerconcentrations, causing mucous secretion and eventual desiccation. Adisadvantage is its dependence on thigh temperature and low humidity forits maximum effect and there is a high recovery rate amongst molluscswhich are able to reverse the water deficit caused by the excess mucoussecretion that metaldehyde stimulates. Under optimal conditions, slugsimmobilized and desiccated by metaldehyde will not survive if trapped inthe open and exposed to sunlight. Unfortunately, it is under dampconditions and at lower temperatures when metaldehyde is least effectivethat terrestrial slugs and snails are most active and yet, at highertemperatures, snails are aestivating and not feeding. There is only avery limited period of time during which snails are feeding and thetemperature is thigh enough for metaldehyde to be effective.

In the mid 1960s, it was found that carbamate compounds such as methylcarbamate were as toxic to molluscs as metaldehyde. Carbamate compoundscause inhibition of cholinesterases which are the enzymes involved insynaptic nervous transmission in a wide range of animals and their modeof action on insect pests has been extensively studied, particularly inconnection with the development of resistance. The methyl carbamate mostwidely used as a molluscicide is methiocarb(3,5-dimethl-1,4-methylthiophenyl-N-methylcarbamate). The effectivenessof methiocarb is compromised less by low temperatures and high humiditythan metaldehyde which is a major advantage, since pest damage oftenoccurs in conditions where metaldehyde is least well suited. However,methiocarb (an active insecticide and acaricide) is more toxic tonon-target organisms such as beneficial insects and earthworms thanmetaldehyde. Although farmers presently tend to use methiocarb, theywould prefer not to because of these highly poisonous characteristicsand the fact that sheep often graze in areas that require treatment forsnails and slugs. For example, in South Australia there areflood-irrigated pastures for sheep and recently, a high incidence of theconical variety of snail, Cochlicella barbara, has been detected.Therefore, any effective molluscicide used under these conditions wouldhave to be effectively water-proofed in addition to not being toxic tothe sheep. Methiocarb is effective on Theba pisana but in view of itsinsecticidal activity and toxicity to earthworms, its use for this snailvariety also has severe drawbacks.

There is considerable evidence to indicate that metal salts used ascontact poisons are toxic to molluscs (Glen, D. M. and Orsman, I. A., in"Comparison of molluscicides based on metaldehyde, methiocarb andaluminum sulphate," Crop Protection, (1986), 5, 371-375.) In particular,iron and aluminum salts have been investigated in this regard in somedetail in the United Kingdom (Henderson et al, "Aluminum(III) andlron(III) complexes exhibiting molluscicidal activity," AustralianPatent AU-B-22526/88). These workers concluded that the effectiveness ofthe molluscicide was dependent on a number of variables but thechelating of the trivalent iron gave very significantly better resultsthan the unchelated salts. In addition, these workers found that theinclusion of the poison in a bait, as a pellet, gave significantlybetter results than the direct application of molluscicide to the soilor application of the bait as a powder to the soil. Details of the baitformulation were given without discussion of differences that might beexpected from other formulations. Such differences are most probablysignificant in determining the amount of chelate required for effectivecontrol. In field conditions, the efficacy and activity of many metalsalts is greatly attenuated by both dilution and the metal ions becomingchemically bound in the soil and being unavailable for toxic action.Proposed contact-action metal poisons such as aluminumtris(acetylacetonate) ("Al(acac)")₃ are expensive to manufacture and aretherefore not economically feasible for use in the home garden or forhorticulture or broad-acre application. Various metal salts are marketedas contact molluscicides and are indeed toxic, but it is debatablewhether they are effective under field conditions. As contact-actionpoisons, they are insufficiently persistent and too repellent to be usedin baits. For these reasons, molluscicides used against terrestrial (asopposed to aquatic) targets are usually delivered in the form ofstomach-action poisons in baits.

One of the other major problems with stomach-action poisons in that theyare often consumed by non-target organisms such as domestic animals,birds and children. In normal agricultural and veterinary applications,the preparations are usually very dilute when applied. However, whenbaits are used this is not the case and there is always a possibilitythat the bait will be consumed by a non-target organism. Accidentalpoisoning of non-target organisms is particularly common in the case ofsnail and slug bait pellets. It is hard to arrive at a reliable figurefor poisoning of dogs, cats and native animals, but in Australia about10,000 poisonings per annum with perhaps as high as 40-50% being fatalis probably a reasonable estimate. A requirement accordingly exists formolluscicides which are effective against snails and slugs, but whichsubstantially minimize the health and environmental risks and costlimitations of the molluscicides currently available on the market.

There are a number of published efficacy trials which indicate thatFerric sodium EDTA (Iron(III) EDTA or ferric EDTA) salt is an effectivecontact-action molluscicide. Research has been conducted on a number ofiron and aluminum compounds as contact poisons against the slugDeroceras reticulatum (Henderson, I. F. and Martin, A. P., in "Controlof slugs with contact-action molluscicides," An. Appl. Biol., (1990),116, 273-278). These workers reported two types of experiments, one inwhich the slugs were confined to a treated glass surface and one usingwet soil in a laboratory test. Unchelated salts were effective poisonswhen applied to a glass surface, but were rapidly deactivated whenapplied on wet soil. Chelation of both metals with organic licandsretarded the rate of attenuation on wet soil. These workers alsoreported a field trial in which chelated iron in a broadcast applicationapplied at 40 kg active ingredient per hectare, or in a bait formulationapplied at 1.32 kg/ha of active ingredient was effective againstDeroceras reticulatum and Arion spp. They concluded that "on theavailable evidence, the bait formulation was apparently more efficient,an application rate of 1.32 kg active ingredient leaving 586 slugs deadon the surface within three days while with the broadcast formulationapplied at 40 kg active ingredient per hectare, only 204 were recordeddead on the surface in the same period." Iron(III) 2,4-pentanedionateappears to be more toxic than Iron(III) EDTA and although it isdifficult to quantify the difference, it appears that on wet soil after10 days, the 2,4-pentanedione is about twice to three times as toxic.Details of the bait formulation were not given but these are mostprobably significant in determining the amount of chelate required foreffective control.

SUMMARY OF THE INVENTION

The inclusion of metal chelates as the active ingredient instomach-action poisons in accordance with the invention, however, offersconsiderable advantages over the presently used stomach-actionmolluscicides, metaldehyde and methiocarb. The present inventionconcerns the inclusion of a complexone as the chelating litgand tofunction as the active ingredient in stomach-action poisons. Selectedcomplexones are considerably less toxic to mammals than methiocarb ormetaldehyde. Indeed, they are used in medical applications to relieveanemia. Such complexones are often used in trace-element mixes insituations where a plant is suffering from an iron deficiency. Theeffectiveness of such complexones is not very temperature- orhumidity-dependent, being comparable with methiocarb in this respect.They are neither insecticides nor acaracides and snail and slug pelletsbased on such compounds will not kill earthworms or the (mainlybeneficial) carabid beetles. The term "metal complexone" is used hereinin its broadest sense and refers to a chelate of a metal with at leastone ligand of the complexone type.

The term "complexone" as used herein refers to an organic ligandcontaining at least one iminodiacetic group --N(CH₂ CO₂ H)₂ or twoarinoacetic groups --NHCH₂ CO₂ H which form stable complexes with mostcations. Suitable complexones include those disclosed in Wilkinson, G.,"Comprehensive Coordination Chemistry", Volume 2, Chapter 20.3, pp777-792 which is incorporated herein by reference.

preferably, the complexone is a derivative of ethylenediaminetetraaceticacid (hereinafter referred to s "EDTA") as shown in formula (I) below:##STR1## wherein n is an integer, preferably from 1 to 6.

Other examples of suitable complexones include those having more thanfour acetic acid residues as shown in formula (II) below: ##STR2##wherein n is an integer, preferably from 1 to 3 or as shown in formula(III) below: ##STR3## wherein n and m are integers, preferably from 1 to4.

While the major complexone utilized in the present invention is EDTA,other complexones, in particular, those having substituents such ashydroxy groups which coordinate to the metal ion more strongly, such asEDDHA, or those which display increased stability due to the presence ofan additional coordinating group, such as DPTA, have also been utilizedin the trials. Other chelates investigated include ferric sodiumethylenediaminebis[(2-hydroxyphenyl)acetic acid] ("FeEDDTA") and ferricsodium diethylenetriaminetetraacetic acid.

According to one aspect of the present invention, there is provided astomach-action molluscicide which includes a metal complexone as anactive ingredient.

Preferably, the metal complexone includes hydroxy- and non-hydroxy-metalcomplexones. Most preferably, the active ingredient is an hydroxy-metalcomplexone.

Typically, the stomach-action molluscicide has a pH above 7. Preferably,the pH is between about 7 and 10. Most preferably, the pH of themolluscicide is about 8.

Typically, the metal of the metal complexone is selected from the groupof Group 2 metals, transition metals or Group 13 metals. Preferably, themetal is selected from the group of magnesium, aluminum, manganese,iron, copper or zinc.

Preferred metal complexones include iron(II) and iron(III), copper andzinc EDTA. Iron EDTA and copper EDTA are preferred with iron EDTA beingthe most preferred. Iron EDTA is also not harmful to the environment asit is widely used as a source of iron for plants and to a limited extentanimals in horticulture and agriculture

Typically, the complexone comprises at least one iminodiacetic group ortwo aminoacetic groups, the complexone forming a stable complex with themetal. Preferably, the complexone has at least four acetic acid groups.More preferably, the complexone is ethylenediaminetetraacetic acid(EDTA). Most preferably, the active ingredient in the molluscicide isthe hydroxy-metal complexone, [Fe(OH)EDTA]Ca which can dimerise to give[EDTAFe-O-FeEDTA]. 2Ca. Anions [Fe(OH)EDTA]²⁻ and [EDTAFe-O-FeEDTA]⁴⁻are important species and it appears that the inclusion of Ca²⁺ isadvantageous as it eventually replaces the chelated iron.

In a preferred form of the present invention, the molluscicide isadvantageously presented in the form of a stomach poison together with acarrier. The carrier usually includes a mollusc food such as a cereal,for example, wheat flour, bran, arrowroot or rice flour; carrot; beer;rice hulls; comminuted cuttle fish; starch or gelatin so that themollusc is attracted to the edible bait. Non-nutrient carriers ofinterest include non-nutrient polymeric materials, pumice, carbon andmaterials useful as carriers for insecticides. The poison or bait mayalso contain other additives known in the art such as molluscphatgostimulants for example sucrose or molasses; lubricants such ascalcium or magnesium stearate, talc or silica; binders which aresuitably waterproof, such as paraffin wax, white oil or casein; andflavoring agents such as BITREXt® which imparts a bitter taste andrenders the poison or bait less attractive to non-target organisms. Inorder to inhibit deterioration of the poison or bait, preservatives suchas sodium benzoate, vitamin E, alpha-tocopherol, ascorbic acid, methylparaben, propyl paraben or sodium bisulphite may also be included.Preferably further, the waterproofing agent comprises a fatty acidalcohol in an amount about between 1% to 5% by weight of the totalcomposition of the poison. More preferably, the fatty acid alcohol isselected from the group of C₁₆ -C₁₈ fatty acid alcohols. Mostpreferably, the C₁₆ -C₁₈ fatty acid alcohols comprises about 5% byweight of the total composition of the poison and the C₁₆ -C₁₈ fattyacid alcohol is HYDRENOL MY manufactured by Henkel Corporation. Thewaterproofing of the bait is also believed to be improved if the densityof the bait is increased since the less porous the composition, the moreeffectively waterproofed it becomes.

To improve the density of the acual mixture before pelletising to reducethe airborne content and thus wastage of the mixture, a filler is addedto the carrier. Preferably the filler is either CaCO₃ or K₂ CO₃.Typically, the poison or bait contains about above 1% and not exceeding5% of a metal carbonate as a filler. When the metal carbonate is CaCO₃,the preferred concentration is about 2-3% by weight. When the metalcarbonate is K₂ CO₃, the preferred concentration is about 4-5% byweight. A combination of CaCO₃ and K₂ CO₃ may also be used.

Serendipitously, such a metal carbonate additionally serves to adjustthe pH of the poison or bait and it was found that the efficacyincreased with an increase in pH. It was found through trials carriedout using various amounts of CaCO₃ and K₂ CO₃ combined, that a balanceneeds to be struck between the pH and the attractiveness of the bait tothe molluscs. If the bait is too acidic, it has been found that theefficacy is reduced. Conversely, if the bait is too alkaline this alsodeters feeding. Typically, the poison or bait has a pH about above 7 andnot exceeding 10. Preferably, the pH of the poison or bait is about 8.Preferably, the agent used to adjust the pH is K₂ CO₃ together withCaCO₃ . A stomach poison having a neutral or alkaline pH has proved tobe more efficacious than one having an acidic pH. The K₂ CO₃, togetherwith the CaCO₃, used as a filler and which adjusts the pH to about above8, aids in the formation of the active ingredient, [Fe(OH)EDTA]Ca. Theperson skilled in the art will appreciate that the behavior of ferricEDTA in solution and at equilibrium is strongly determined by itsspeciation. At a pH of between 7 and 10, the species present in themajority is [Fe(OH)EDTA]²⁻ with [Fe(tEtH) EDTA]⁻ being present in theminority. According to F. G. Kari et al, Environ. Sci. Technol., (1995),29, 1008, at a pH of about 8 to 8.5, there is virtually no [Fe(III)EDTA]⁻ species present at all.

Preferably, the active ingredient comprises at least 6% by weight of thetotal composition of the molluscicide. More preferably, the activeingredient comprises about 6% to about 12% by weight of the totalcomposition of the molluscicide when the active ingredient is[Fe(OH)EDTA]Ca or its dimer[EDTAFe-O-FeEDTA]. 2Ca. Most preferably,[Fe(OH)EDTA]Ca comprises about 9% by weight of the total composition.

According to yet another aspect of the invention, the active ingredientcomprises a metal complexone in combination with at least one othermolluscicide. Typically, the other molluscicide is selected frommetaldehyde or methiocarb, wherein the other molluscicide is in asynergistic relationship with the metal complexone.

The molluscicide is advantageously presented in a solid form such astablets, powders, granules or pellets. Those skilled in the art willappreciate that it is preferable to prepare the products the subject ofthe invention in a form that is easy for consumers to use. Pellets, forexample, can be easily scattered from a box across the area to beprotected. Preferably, the molluscicide is in the form of a pellet. Morepreferably, the pellet is between 2.5 and 4 mm long. Most preferably,the pellet is 3 mm long.

According to another aspect of the invention, the method of preparationof the stomach-action molluscicide in pellet form includes the steps of:

(i) blending the molluscicide and elements of the carrier together toform a blended composition;

(ii) heating the blended composition for about 1 to 5 minutes in thepresence of steam at an ambient temperature of between about 80 and 100°C.;

(iii) maintaining the blended composition at the ambient temperature forbetween 10 and 30 seconds; and

(iv) forming the blended composition into one or more pellets.

Preferably, step (ii) is carried out at about 90° C. for about 2minutes, whereafter step (iii) is carried out for about 15 seconds.Preferably, the blended composition is formed into pellets by extrusion.

The term "stomach-action molluscicide" is used herein in its broadestsense and includes a molluscicide which is capable of being ingestedinto the stomach of the mollusc in an effective amount so as to killand/or inactivate the mollusc.

EXAMPLES

The invention will now be illustrated with reference to the followingnon-limiting Examples.

Study of the Effectiveness of Fe EDTA Pellets and Powder Compared withMetaldehyde and Methiocarb Pellets

The first set of examples are where the product which is the subject ofthe present invention, was tested and compared with other productscurrently registered and in the Australian market place and otherrepresentative products available elsewhere in the world. The mostcommonly used home garden pellets in Australia based on metaldehyde aresold under the brand name of DEFENDER™. It may be argued that DEFENDERt™pellets which contain 1.5% metaldehyde are not the best metaldehydepellets available. However, additional trials using pellets containing6% metaldehyde have also been carried out and very similar results wereobtained. Additional trials have also been carried out comparing theproduct of the present invention with methiocarb-based pellets.Methiocarb-based pellets account for about 20% of pellets used inAustralia and are widely used elsewhere in the world.

The baits, which are the subject of the present invention, are based onbran/wheat flour and are typical of common baits used throughout theworld. The known attractiveness of bran/wheat flour baits in theindustry made it unnecessary for further experimentation in this area.

To test the efficacy of the baits, which are the subject of the presentinvention, experiments were set up keeping the following variables inmind:

(i) bait formulation;

(ii) soil type;

(iii) concentration of the active ingredient;

(iv) species of mollusc; and

(v) temperature (range of maximum daily temperature).

Two different bait formulations were used, the first, low bran type,consisted of bran and wheat flour in the ratio of 1 part bran to 4 partsflour, together with small amounts of calcium stearate as a dielubricant, a binder, a filler and a mould inhibitor The second, highbran type consisted of wheat flour and bran in approximately equalproportions by weight together with a small amount of oat meal(lubricant), a small proportion of sugar (1-2%), a filler and a mouldinhibitor. The control treatment involved providing the snails and slugswith carrot for food unless otherwise specified.

The composition of the Fe EDTA pellets and powder was as follows:

655 g/kg wheat flour (for low bran) or 380 g/kg wheat flour (for highbran);

160 g/kg bran ("low bran") or 315 g/kg bran("hiah bran");

20 g/kg oat meal (high bran)

20 g/kg calcium stearate;

90 g/kg ferric sodium EDTA;

20 g/kg CaCO₃ ;

5 g/kg K₂ CO₃

20 g/kg sodium benzoate;

0.2 g/kg BITREX® (denatonium benzoate): and

40 g/kg white oil.

It was established in a number of preliminary trials that ferric EDTAwas toxic to Helix aspersa and Deroceras retictilatum as a contactpoison on a smooth glass surface. Subsequent trials compared theeffective toxicity of methiocarb, metaldehyde bait pellets and ferricEDTA pellets and ferric EDTA bait powder to Helix aspersa and theeffective toxicity of ferric EDTA to Deroceras reticularum. Limitedtrials were carried out on Theba pisana (the white Italian snail),Cernutmella virgata (the vineyard snail), Limax maximus and Cochliceilaspp. These trials confirmed that the particular bait formulationtogether with 8.5-9% ferric EDTA was effective in control of molluscs.

There are many possible variables to consider when evaluating snail orslug pellets. Field trials are often poorly controlled and it is oftendifficult to arrive at unambiguous conclusions. It is possible to applyextensive statistical analysis to poorly designed or controlledexperiments. However, a series of simple experiments in which thevariables are controlled lead to unambiguous conclusions with no needfor detailed statistical analysis. It was decided to compare the pelletsunder laboratory conditions which could closely mimic controlled fieldconditions but would not present problems arising from incompletecollection and counting of dead specimen or non-uniform distribution ofsnails in the trial patches. No attempt was made to control the diurnaltemperature or the length of daylight, even though it was known thatthese factors do play some part in snail and slug feeding activity buttheir role is minor compared with the effect of temperature.

It should be noted that trials on slugs are particularly difficult onaccount of three factors. Firstly, it is difficult to distinguishbetween moribund and dead slugs. Secondly, slugs bury themselves in soiland it is often difficult to find dead slugs which have decomposed.Thirdly, it is believed that bacteria from dead slugs often infect andsubsequently kill other slugs.

In this study two types of "plot" were employed. The first type of plotconsisted of about 1 cm depth of sandy loam or potting mix placed in aseed tray of approximate dimensions 30×25 cm. The top was covered with a3 mm glass sheet of which about 70% was covered with black, polythenefilm. The polythene film was attached with adhesive tape (on theoutside), so that the snails or slugs were able to rest on a smoothsurface out of direct sunlight. For the second type of plot, apolycarbonate "food storage container" of 175 mm diameter and 80 mmheight was employed, four air holes of 2 mm diameter were made in thelid of each container. These containers were used as it was thoughtthat, in the case of Theba pisana, Cernuella virgata and Cochlicellabarbara eggs might be laid in the soil and if the seed trays were usedextensive precautions were necessary to avoid introducing these snailsto areas where they were not previously established. The smallercontainers were used to study Deroceras reiculatuin and the soilreplaced by a layer of absorbent paper or a thin layer of soil. Thisprocedure was used because slugs often buried themselves in the soil andwere difficult to find without disturbing the soil. It was oftendifficult to establish if buried slugs were alive or dead.

Unless otherwise specified, the common garden snail, Helix aspersa wasused in the Examples. The control treatment involved providing thesnails and slugs with food, carrot and cabbage leaves in Example 1 andcarrot in the remaining Examples. The effectiveness of slug pellets onmoist potting mix was studied during spring under natural climaticconditions. In this period, snails were active in the garden as a resultof a cool damp spell. While the ideal feeding temperature for snails andslugs is around 20° C., the temperature should be about above 10° C.because at temperatures below this, feeding is considerably reduced.

In Examples 1 to 4, Fe EDTA pellets and powder were compared withmetaldehyde pellets marketed under the trade name DEFENDER™. DEFENDERt™pellets contain 1.5% metaldehyde. The pellets were compared underlaboratory conditions which would closely mimic controlled fieldconditions, but would not present problems arising from incompletecollection and counting of dead specimens or non-uniform distribution ofsnails in the trial patches.

Example 1

This Example involved 3 replicate "plots" of 4 different treatments.Each "plot" consisted of a 250×300 plastic tray containing moist pottingmix which was covered by a sheet of glass. Black polythene which coveredabout 65% the top of the tray was placed over the glass sheet so that itprovided a refuge for the snails. About 50 grams of fresh carrot slicesand 100 grams of fresh cabbage leaves were placed on top of the moistpotting mix in opposite comers of each of the twelve seed trays. Sixsnails were placed in one of the other corners of each of the twelveseed trays at dusk. Metaldehyde pellets were spread more or lessuniformly across three of the trays and the Fe EDTA pellets weresimilarly spread across three other trays. In the other three trays, FeEDTA powder was spread about 3-5 cm away from the sliced carrot andcabbage leaves. The snails were observed after 3 days and 6 days withany dead snails being removed and their numbers noted. It was difficultto establish whether some of the snails were dead or merely poisoned andinactive. Only those snails which appeared to be decomposing werecounted. The results are given in Table 1 below. It was noticed that theamount of food remaining in the three (×3) treatment plots was greaterthan in the control. This was not assessed quantitatively. Since afterthree days the number of active snails in the control plots were onaverage more than double that in the treatment plots, it would bemisleading, to assert that the feeding of active snails was reduced.Obviously dead snails did not consume food and live, but poisonedinactive snails did not consume much if any food.

                  TABLE 1                                                         ______________________________________                                        Comparison of efficacy of Fe EDTA pellets and                                 powder with metaldehyde.                                                      ______________________________________                                        Control        1/6   0/6       0/6  1/18                                      Metaldehyde    2/6   3/6       5/6 10/18                                      Fe EDTA pellets                                                                              3/6   3/6       6/6 12/18                                      Fe EDTA powder 2/6   2/6       3/6  7/18                                      ______________________________________                                    

Example 2

This Example was the same as Example 1 except that no powder treatmentwas involved and each treatment was replicated four times. Furthermore,the food used was only about 100 g of freshly sliced carrot with nocabbage leaves being included. The number of snails after 6 and 8 dayswere recorded and are given in Table 2 below. The average dailytemperature of this trial was about 5° C. cooler than in Example 1. Theresults show that the effectiveness of metaldehyde as a poison is verytemperature sensitive whereas for ferric EDTA, the main effect is due toa decrease in general activity such as feeding which causes the kill tobe somewhat slower than in Example 1. Ferric EDTA is clearly very muchmore effective at lower temperatures than metaldehyde pellets.

                  TABLE 2                                                         ______________________________________                                        Comparison of the efficacy of Fe EDTA pellets with                            metaldehyde at low temperature                                                ______________________________________                                        Control     0/6      0/6   0/6    0/6 0/24                                    Metaldehyde 1/6      0/6   2/6    0/6 3/24                                    Fe EDTA pellets                                                                           4/6      5/6   5/6    6/6 20/24                                   ______________________________________                                    

Example 3

This Example was conducted using Zeneca (metaldehyde), BIO® PBI(metaldehyde) and 9% Fe EDTA within a temperature range of 18-29° C.using carrot as the feed and high bran in the bait formulation. The deadsnails were removed and counted after 7 days. The results are shown inTable 3.

                  TABLE 3                                                         ______________________________________                                        Comparison of the efficacies of different brands of metaldehyde               with 9% Fe EDTA.                                                              ______________________________________                                        Control       0/3   0/3   0/3 0/3 0/3 0/3 0/3 0/3  0/24                       Zeneca (Metaldehyde)                                                                        2/3   3/3   2/3 3/3 1/3 2/3 2/3 1/3 16/24                       BIO ® PBI (Metaldehyde)                                                                 0/3   1/3   1/3 1/3 0/3 2/3 0/3 2/3  7/24                       9% Fe EDTA    3/3   3/3   3/3 2/3 3/3 3/3 3/3 3/3 23/24                       ______________________________________                                    

Example 4

This Example was the same as Example 2, except that the treatments werecontrol, metaldehyde, methiocarb marketed by Yates and 9% Fe EDTA. Theresults are given in Table 4 below. The weather conditions were warm anddry and there was considerably less snail activity than in Example 2.The lower kill rate was expected as the amount of feeding was reduced.

                  TABLE 4                                                         ______________________________________                                        Comparison of the efficacies of meltaldehyde,                                 methiocarb and 9% Fe EDTA.                                                    ______________________________________                                        Control        0/6   0/6       0/6 0/18                                       Metaldehyde    4/6   4/6       4/6 12/18                                      Methiocarb     3/6   2/6       3/6 8/18                                       Fe EDTA pellets                                                                              2/6   3/6       4/6 9/18                                       ______________________________________                                    

Summary

Examples 1 to 4 show that the Fe EDTA pellets worked well, themetaldehyde pellets worked moderately well, but the methiocarb and theFe EDTA powder was less effective. However when using very moist pottingmix fairly poor results for the powder would be expected as it woulddissolve in the moisture and be taken up by the soil.

In Example 5, the efficacy of various concentrations of Fe EDTA weretrialed.

Example 5

This Example was the same as Example 4, except that the treatments werecontrol and pellets containing 1%, 2.5%, 6%, 9%, 12%, 16% and 20% FeEDTA. The results are given in Table 5 below. The weather conditionswere warm and dry and there was considerably less snail activity than inExample 2. Dead snails were removed and counted after 6 days. The lowerkill rate (compared to Example 2) was expected as feeding was reduced.

                  TABLE 5                                                         ______________________________________                                        Comparison of the efficacies of varying concentrations                        of Fe EDTA used in the pellets.                                               ______________________________________                                        Control       0/6   0/6       0/6 0/18                                        Fe EDTA 1%    2/6   0/6       1/6 3/18                                        Fe EDTA 2.5%  0/6   0/6       1/6 1/18                                        Fe EDTA 6%    2/6   2/6       4/6 8/18                                        Fe EDTA 9%    2/6   3/6       4/6 9/18                                        Fe EDTA 12%   3/6   3/6       5/6 11/18                                       Fe EDTA 16%   3/6   4/6       3/6 10/18                                       Fe EDTA 20%   6/6   3/6       4/6 13/18                                       ______________________________________                                    

Summary

The results of Example 5 indicate that the proposed 9% Fe EDTA isappropriate. Slightly higher concentrations may give slightly higherkill rates but the effect is marginal. It is interesting to note thateven at 20%, the kill rate is high. This can only be the case if thepellets are still palatable with this high concentration of activeingredient. Pellets of even higher concentration are difficult tomanufacture without using additional binders.

In the following two Examples, the effect of varying the metal ion wasinvestigated. In Example 7, the effect of varying the concentration ofcopper EDTA was invest gated.

Summary

Examples 1 to 4 show that the Fe EDTA pellets worked well, themetaldehyde pellets worked moderately well, but the methiocarb and theFe EDTA powder was less effective. However when using very moist pottingmix fairly poor results for the powder would be expected as it woulddissolve in the moisture and be taken up by the soil.

In Example 5, the efficacy of various concentrations of Fe EDTA weretrialed.

Example 5

This Example was the same as Example 4, except that the treatments werecontrol and pellets containing 1%, 2.5%, 6%, 9%, 12%, 16% and 20% FeEDTA. The results are given in Table 5 below. The weather conditionswere warm and dry and there was considerably less snail activity than inExample 2. Dead snails were removed and counted after 6 days. The lowerkill rate (compared to Example 2) was expected as feeding was reduced.

                  TABLE 5                                                         ______________________________________                                        Comparison of the efficacies of varying concentrations                        of Fe EDTA used in the pellets.                                               ______________________________________                                        Control       0/6   0/6       0/6 0/18                                        Fe EDTA 1%    2/6   0/6       1/6 3/18                                        Fe EDTA 2.5%  0/6   0/6       1/6 1/18                                        Fe EDTA 6%    2/6   2/6       4/6 8/18                                        Fe EDTA 9%    2/6   3/6       4/6 9/18                                        Fe EDTA 12%   3/6   3/6       5/6 11/18                                       Fe EDTA 16%   3/6   4/6       3/6 10/18                                       Fe EDTA 20%   6/6   3/6       4/6 13/18                                       ______________________________________                                    

Summary

The results of Example 5 indicate that the proposed 9% Fe EDTA isappropriate. Slightly higher concentrations may give slightly higherkill rates but the effect is marginal. It is interesting to note thateven at 20%, the kill rate is high. This can only be the case if thepellets are still palatable with this high concentration of activeingredient. Pellets of even higher concentration are difficult tomanufacture without using additional binders.

In the following two Examples, the effect of varying the metal ion wasinvestigated. In Example 7, the effect of varying the concentration ofcopper EDTA was investigated.

In Example 8, the efficacy of a different metal chelate Fe EDDtFLA wascompared to Fe EDTA.

Example 8

This Example was the same as Example 2, except that Fe EDDHA was alsotested. The average daily maximum temperature was about 25° C. and thepotting mix was kept moist by the addition of a 50 ml of water once aday. The dead snails were removed and counted after 8 days. The resultsare shown in Table 8 below.

                  TABLE 8                                                         ______________________________________                                        Comparison of the efficacies of 10% Fe EDDHA with 10% Fe                      ______________________________________                                        EDTA                                                                          Control     1/6      0/6   0/6    0/6 1/24                                    10% Fe EDDHA                                                                              3/6      2/6   0/6    3/6 8/24                                    10% Fe EDTA 3/6      2/6   4/6    4/6 13/24                                   ______________________________________                                    

Summary

From this result, it can be seen that Fe EDTA is far more effective thanFe EDDHA.

In Examples 9 to 11, the efficacy of different bait compositions andpellet size was compared.

Example 9

This Example used low bran formulation in two different sizes of pelletcompared with a high bran formulation as against a control containing noactive ingredient. Four different "plots" containing moist potting mixwere used. The weather condition for this trail were warm and dry. Thedead snails were collected and counted after 7 days. The results areshown in Table 9.

                  TABLE 9                                                         ______________________________________                                        Comparison of efficacies of different bait compositions and pellet            ______________________________________                                        size.                                                                         Control          0/6    0/6    0/6  0/6   0/24                                Formulation 1 (low bran) 2 mm                                                                  5/6    6/6    3/6  5/6  19/24                                Formulation 2 (low bran) 3.5 mm                                                                4/6    5/6    6/6  5/6  20/24                                Formulation 3 (low bran) 2 mm                                                                  5/6    3/6    3/6  6/6  17/24                                Formulation 4 (high bran) 3.8 mm                                                               5/6    5/6    5/6  5/6  20/24                                ______________________________________                                    

Example 10

This Example was the same as above except that moist sandy loam wasused. The difference in medium appeared not to greatly alter the resultsobtained. However, a higher kill rate was observed when using a pelletsize of around 3.5 mm, irrespective of the bait formulation used. Thedead snails were collected and counted after 8 days. The results areshown in Table 10.

                  TABLE 10                                                        ______________________________________                                        Comparison of efficacy of different bait compositions and pellet              ______________________________________                                        size.                                                                         Control          0/6    0/6    0/6  0/6   0/24                                Formulation 1 (low bran) 2 mm                                                                  5/6    5/6    3/6  5/6  18/24                                Formulation 2 (low bran) 3.5 mm                                                                4/6    5/6    6/6  5/6  20/24                                Formulation 3 (low bran) 2 mm                                                                  5/6    3/6    3/6  6/6  17/24                                Formulation 4 (high bran) 3.8 mm                                                               5/6    5/6    5/6  5/6  20/24                                ______________________________________                                    

Example 11

This Example utilized three "plots" which contained moist potting mix.The weather conditions were much cooler than the above two Examples. Alow bran formulation contained in a small pellet and a high branformulation contained in a larger pellet were compared to metaldehydeand methiocarb. The results are shown in Table 11.

                  TABLE 11                                                        ______________________________________                                        Comparison of the efficacies of metaldehyde,                                  methiocarb and Fe EDTA pellets.                                               ______________________________________                                        Control             0/6    0/6    0/6   0/18                                  Bran formulation 1 (low bran) 2 mm                                                                4/6    4/6    3/6  11/18                                  Bran formulation 4 (high bran) 3.8 mm                                                             4/6    5/6    6/6  15/18                                  Metaldehyde         2/6    0/6    1/6   3/18                                  Methiocarb          4/6    4/6    3/6  11/18                                  ______________________________________                                    

Summary

Examples 9 to 11 show that the low bran formulation of the inventionworked as well as methiocarb, but the high bran formulation of theinvention in the larger pellet was the most effective. Example 11 showsthat metaldehyde does not work as well at the lower temperatures.

In Example 12, the efficacy of Fe EDTA with and without 10% paraffin waxused as a water-proofing agent, was compared to that of metaldehydeunder different weather conditions, while Example 13 compared Fe EDTApellets with and without 10% paraffin wax.

Example 12

For this Example, the bait formulation contained high bran and theweather conditions were cool. After 8 days, the dead snails in each plotwere collected and counted.

The results are shown in Table 12.

                  TABLE 12                                                        ______________________________________                                        Comparison of the efficacies of metaldehyde, Fe EDTA and                      Fe EDTA/10% paraffin wax pellets.                                             ______________________________________                                        Control        0/5   0/5       0/5 0/15                                       Metaldehyde    0/5   0/5       1/5 1/15                                       Fe EDTA        4/5   4/5       4/5 12/15                                      Fe EDTA/10% wax                                                                              2/5   4/5       3/5 9/15                                       ______________________________________                                    

Example 13

This Example was carried out using moist sandy loam contained in four"plots," a high bran formulation and the same weather conditions as inExample 12. The dead snails were collected and counted after seven days.The results are shown in Table 13.

                  TABLE 13                                                        ______________________________________                                        Comparison of efficacy of Fe EDTA pellets with and without                    ______________________________________                                        wax.                                                                          Fe EDTA      4/6      6/6   5/5    5/6 20/23                                  Fe EDTA/10% wax                                                                            5/6      5/6   5/6    3/6 18/24                                  ______________________________________                                    

Summary

The results showed that a lower kill rate was obtained for the pelletscontaining paraffin wax than those without paraffin wax, but the pelletscontaining Fe EDTA and 10% paraffin wax were much more effective thanmetaldehyde.

In Examples 14 and 15, a C₁₆ -C₁₈ alcohol known as HYDRENOL MY, 5% byweight, was incorporated into the high bran bait formulation as awater-proofing agent. In both Examples, trials were carried out in coldweather conditions. The efficacy of Fe EDTA without the water-proofingagent and Fe EDTA including the water-proofing agent were compared withmetaldehyde (1.5%) and methiocarb (2%), respectively in Example 14 andthen with each other in Example 15.

Example 14

In this Example, seven "plots" for each molluscicide formulation and forthe control were used. The variety of snail was Helix aspersa. The deadsnails were collected and counted after 10 days. The results are shownin Table 14.

                  TABLE 14                                                        ______________________________________                                        Comparison of the efficacy of Fe EDTA with and without waterproofing          for Helix aspersa.                                                            ______________________________________                                        Control       0/6   0/6   0/6 0/6 0/6 0/6  0/6   0/42                         Fe EDTA       2/6   2/6   2/6 1/6 2/6 1/6  2/6  12/42                         Fe EDTA + 5% HYD MY                                                                         3/6   1/6   2/6 2/6 2/6 1/6  2/6  13/42                         ______________________________________                                    

Example 15

In this Example, eight "plots" for each molluscicide formulation wereused. The variety of slug used was Deroceras reticitlatum. The deadslugs were collected and counted after 10 days. The number of slugs thatcould not be found are given in brackets. The results are shown in Table15.

                                      TABLE 15                                    __________________________________________________________________________    Comparison of the efficacies of Fe EDTA, Fe EDTA with waterproofing,          metaldehyde and                                                               methiocarb pellets for Deroceras reticulatum.                                 __________________________________________________________________________    Control    0/2                                                                             0/2                                                                             0/2  0/2  0/2  1/2  0/2                                                                             0/2  .sup.   1/16                        Metaldehyde                                                                              2/2                                                                             1/2                                                                             0/2  0/2  1/2  0/2  0/2                                                                             0(1)/2.sup.                                                                         7(1)/16                            Methiocarb 2/2                                                                             2/2                                                                             1/2  2/2  1(1)/2.sup.                                                                        1(1)/2.sup.                                                                        2/2                                                                             1/2  15(1)/16                            Fe EDTA    2/2                                                                             2/2                                                                             1(1)/2.sup.                                                                        0(1)/2.sup.                                                                        2/2  2/2  2/2                                                                             2/2  15(2)/18                            Fe EDTA/5% HYD MY                                                                        2/2                                                                             2/2                                                                             2/2  2/2  1(1)/2.sup.                                                                        2/2  2/2                                                                             2/2  15(1)/16                            __________________________________________________________________________

Summary

Examples 14 and 15 show that the bait formulation including thewater-proofing agent actually worked better than those without. Also,the water-proofed complexone worked as well as methiocarb which bothworked better than metaldehyde. Thus, the inclusion of thewater-proofing agent does not dramatically affect the efficacy of thepresent invention.

In Example 16, the efficacies of various concentrations of Fe EDTA weretrialed on the slug species, Deroceras reticitlattm.

Example 16

In this Example, six "plots" were used under cool weather conditions,using a high bran bait formulation, with carrot as the feed. The soiltype was sandy loam and the slug species was Deroceras reticulatum. Thenumber of dead slugs were collected and counted after seven days. Theresults are given in Table 16.

                  TABLE 16                                                        ______________________________________                                        Comparison of the efficacies of various concentrations of Fe EDTA for         Deroceras reticulatum                                                         ______________________________________                                        Control  0/2      0/2   1/2   0/2 0/2   0/2  1/12                             Fe EDTA 4.8%                                                                           1/2      0/2   1/2   2/2 1/2   2/2  7/12                             Fe EDTA 5.7%                                                                           2/2      1/2   1/2   2/2 2/2   2/2 10/12                             Fe EDTA 9%                                                                             2/2      1/2   2/2   2/2 2/2   2/2 11/12                             ______________________________________                                    

Summary

Fe EDTA at a concentration of 9% was found to be the most effective.

In Examples 17 to 26, trials involving different species of snails andslugs were carried out to test the efficacy of Fe EDTA pellets comparedwith the control. Moist potting mix was used in all Examples.

Example 17

In this Example, three "plots" were used under warm weather conditions.The feed was 20% bran and 80% wheat flour and the bait formulationincluded low bran. The species of snail was Cernuella virgata. The deadsnails were collected and counted after 8 days. The results are shown inTable 17.

                  TABLE 17                                                        ______________________________________                                        The efficacy of Fe EDTA pellets for Cernuella virgata.                        ______________________________________                                        Control      0/5   0/5         0/5 0/15                                       Fe EDTA      2/5   4/5         3/5 9/15                                       ______________________________________                                    

Example 18

In this Example, four "plots" were set up under cooler conditions thanin Example 17. The feed was lettuce and the bait formulation includedhigh bran. The species of snail was Cochlicella spp. The dead snailswere collected and counted after 7 days. The results are shown in Table18.

                  TABLE 18                                                        ______________________________________                                        The efficacy of Fe EDTA pellets for Cochlicella spp.                          ______________________________________                                        Control   1/10      1/10  1/10     2/10                                                                               5/40                                  Fe EDTA  10/10     10/10  9/10    10/10                                                                              39/40                                  ______________________________________                                    

Example 19

In this Example, ten "plots" were set up under similar conditions toExample 18. The feed was bran and the bait formulation included highbran. The species of snail was Theba pisana . The efficacy of Fe EDTA(9%), Fe EDTA (9%)+HYDRENOL MY (5%), metaldehyde (DEFENDER™ brand) andmethiocarb (BAYSOL® brand) were compared to a control. The dead snailswere collected and counted after 13 days. The results are shown in Table19.

                  TABLE 19                                                        ______________________________________                                        Comparison of the efficacies of Fe EDTA (9%) and Fe EDTA (9%) +               waterproof (5%) pellets with methiocarb (BAYSOL ®) and metaldehyde        (DEFENDER ™) for Theba pisana.                                             ______________________________________                                        Control   0/5   1/5   0/5 0/5 0/5 0/5 1/5 2/5 0/5 0/5  4/50                   Methiocarb                                                                              4/5   3/5   4/5 5/5 4/5 5/5 5/5 5/5 3/5 3/5 38/50                   (BAYSOL ®)                                                                Metaldehyde                                                                             4/5   3/5   2/5 4/5 4/5 3/5 4/5 2/5 5/5 5/5 36/50                   (DEFENDER ™)                                                               Fe EDTA (9%)                                                                            4/5   5/5   5/5 5/5 4/5 5/5 5/5 5/5 3/5 4/5 45/50                   Fe EDTA (9%) +                                                                          2/5   2/5   4/5 2/5 3/5 4/5 4/5 3/5 4/5 3/5 31/50                   5% HYD MY                                                                     ______________________________________                                    

Example 20

In this Example, eight "plots" were used in cool weather conditions. Thebait formulation included high bran, while the feed was carrot. Asabove, the species of snail was Theba pisana and the soil was sandyloam. The dead snails were removed and counted after 7 days. The resultsare shown in Table 20.

                  TABLE 20                                                        ______________________________________                                        Comparison of the efficacies of Fe EDTA (2%, 3%, 3.8%, 4.8%, 5.7%,            7.4%, 9%), Q-Fe-6, Fe-Hi, Fe DPTA pellets with methiocarb                     (BAYSOL ®), metaldehyde (DEFENDER ™), metaldehyde                      (DEFENDER ™ Petrepel), metaldehyde (Lonza) for Theba                       ______________________________________                                        pisana.                                                                       Control        0/5   1/5   0/5 0/5 1/5 1/5 0/5   3/35                         Fe EDTA 2%     2/5   1/5   1/5 2/5 4/5 1/5 1/5  12/35                         Fe EDTA 3%     0/5   0/5   3/5 2/5 2/5 1/5 3/5  11/35                         Fe EDTA 3.8%   4/5   2/5   1/5 2/5 0/5 1/5 1/5  11/35                         Fe EDTA 4.8%   2/5   0/5   3/5 0/5 3/5 1/5 1/5  10/35                         Fe EDTA 5.7%   4/5   4/5   3/5 4/5 3/5 3/5 3/5  24/35                         Fe EDTA 7.4%   3/5   3/5   2/5 4/5 2/5 4/5 1/5  17/35                         Fe EDTA 9%     1/5   3/5   5/5 4/5 4/5 3/5 2/5  22/35                         Q-Fe-6         0/5   1/5   0/5 0/5 0/5 0/5 0/5   1/35                         Fe-Hi          1/5   0/5   0/5 0/5 0/5 0/5 0/5   1/35                         Fe DPTA        2/5   2/5   1/5 1/5 0/5 2/5 2/5  10/35                         Methiocarb BAYSOL ®                                                                      1/5   1/5   3/5 3/5 2/5 3/5 0/5  13/35                         Metaldehyde DEFENDER ™                                                                    2/5   2/5   1/5 1/5 0/5 1/5 1/5   8/35                         Metaldehyde DEFENDER ™                                                                    0/5   0/5   2/5 0/5 0/5 1/5 1/5   4/35                         Petrepel                                                                      Metaldehyde Lonza                                                                            2/5   2/5   0/5 1/5 0/5 0/5 0/5   5/35                         ______________________________________                                         Q-Fe-6 is ferric sodium ethylenediamine bis[(2hydroxyphenyl)acetic acid]      (Akzo Chemicals)                                                              FeHi is ferric sodium ethylenediamine bis[(2hydroxyphenyl)acetic acid]        (Allied Colloids)                                                             Fe DPTA is ferric sodium diethylenetriamine pentaacetic acid.            

Example 21

In this Example, seven "plots" were used in cool weather conditions. Thebait formulation included high bran, while the feed was carrot. The soiltype was moist potting mix. The species of snail was Helix aspersa. Thenumber of snails dead after eight days were removed and counted. Theefficacy of Fe EDTA was compared to that of DEFENDER™ Petrepel. Theresults are given in Table 21.

                  TABLE 21                                                        ______________________________________                                        Comparison of the efficacy of Fe EDTA with DEFENDER ™ Petrepel             on Helix aspersa.                                                             ______________________________________                                        Control      0/6   0/6   0/6 0/6 0/6 0/6  0/6  0/42                           DEFENDER ™ Petrepel                                                                     0/6   0/6   1/6 0/6 1/6 0/6  0/6  2/42                           Fe EDTA      4/6   2/6   5/6 0/6 3/6 5/6  1/6  20/42                          ______________________________________                                    

Example 22

In this Example, six "plots" were used in cool weather conditions. Thebait formulation included high bran. The species of snail wasCochlicella barbatra. The efficacy of Fe EDTA was compared with that ofmethiocarb and metaldehyde. The results are shown in Table 22.

                  TABLE 22                                                        ______________________________________                                        Comparison of the efficacies of Fe EDTA, methiocarb and metaldehyde           pellets for Cochlicella barbara.                                              ______________________________________                                        Control 2/10   1/10   2/10 2/10  3/10  3/10  12/60                            Methiocarb                                                                            6/9    8/10   6/10 6/10  8/10  5/10  39/59                            Metaldehyde                                                                           7/10   2/10   3/10 7/10  3/9   4/10  26/59                            Fe EDTA 8/10   5/9    5/9  7/10  6/10  7/10  38/58                            ______________________________________                                    

Example 23

In this Example, six "plots" were used under warm weather conditions.The bait formulation included low bran. The species of slug wasDeroceras reticulatum. The dead slugs were collected and counted after 8days. The results are shown in Table 23.

                  TABLE 23                                                        ______________________________________                                        The efficacy of Fe EDTA pellets for Deroceras reticulatum.                    ______________________________________                                        Control  1/6     1/6   1/6   1/6 1/6   1/6  5/36                              Fe EDTA  6/6     6/6   6/6   6/6 6/6   6/6 36/36                              ______________________________________                                    

Example 24

In this Example, six "plots" were used in moderate to warm weatherconditions. The bait formulation included high bran. The species of slugwas Limax maximus. The dead slugs were collected and counted after 7days. The results are shown in Table 24.

                  TABLE 24                                                        ______________________________________                                        The efficacy of Fe EDTA pellets for Limax maximus.                            ______________________________________                                        Control  0/6     0/6   0/6   0/6 0/6   0/6  0/36                              Fe EDTA  6/6     6/6   6/6   6/6 6/6   6/6 36/36                              ______________________________________                                    

Example 25

In this Example, juvenile slugs of Deroceras reticulatum, being 1 to 2cm long were subjected to Fe EDTA. The number of dead slugs werecollected and counted after 9 days. The number in brackets denotes thenumber of slugs that were not found. The results are shown in Table 25.

                  TABLE 25                                                        ______________________________________                                        The efficacy of Fe EDTA pellets for juvenile slugs.                           ______________________________________                                        Control                                                                              0(2)/2.sup.                                                                            0/2      0/2  0/2  0(2)/2                                                                              0/2 0(4)/12                          Fe EDTA                                                                              2/2      1(1)/2.sup.                                                                            2/2  2/2  1(1)/2                                                                              1/2 9(2)/12                          ______________________________________                                    

Summary

The results show that Fe EDTA is effective even for all molluscs trialedincluding juvenile slugs.

In Examples 26 and 27, the efficacy of Fe EDTA (9% in a high branformulation) is compared to other well-known brands of snail and slugkillers containing methiocarb or metaldehyde. In both Examples, coolweather conditions were employed.

Example 26

In this Example, the efficacy of Fe EDTA was compared with that ofBlitzem made by Yates (1.5% metaldehyde), Lonza (6% metaldehyde) andBAYSOL® made by Bayer (2% methiocarb). The dead snails were collectedand counted after 8 days. The results are shown in Table 26.

                  TABLE 26                                                        ______________________________________                                        Comparison of the efficacy of Fe EDTA with that of metaldehyde (1.5%),        metaldehyde (5%) and metaldehyde (6%).                                        ______________________________________                                        Control  0/6   0/6   0/6 0/6 0/6 0/6 0/6 0/6 0/6 0/6 0/60                     Metaldehyde                                                                            1/6   0/6   0/6 0/6 0/6 0/6 0/6 0/6 0/6 0/6 1/60                     (1.5%) Blitzem                                                                Metaldehyde                                                                            0/6   1/6   1/6 1/6 1/6 0/6 0/6 0/6 1/6 0/6 5/60                     (6%) Lonza                                                                    Methiocarb                                                                             3/6   2/6   1/6 4/6 4/6 2/6 3/6 2/6 3/6 2/6 26/60                    (2%)                                                                          BAYSOL ®                                                                  Fe EDTA  4/6   4/6   5/6 4/6 1/6 1/6 4/6 3/6 4/6 4/6 38/60                    ______________________________________                                    

Example 27

In this Example, the efficacy of Fe EDTA was compared with that of BIO®Slug-Gard (4% methiocarb, a UK product) and GARDENER'S CHOICE™(metaldehyde, a brand available in K-Mart stores) for Helix aspersa. Thedead snails were collected and counted after 10 days. The results areshown in Table 27.

                  TABLE 27                                                        ______________________________________                                        Comparison of the efficacies of Fe EDTA, metaldehyde and methiocarb           pellets for Helix aspersa.                                                    ______________________________________                                        Control      0/6   0/6   1/6 0/6 0/6 0/6 0/6 0/6   1/48                       Metaldehyde  1/6   0/6   0/6 0/6 0/6 0/6 1/6 0/6   2/48                       GARDENER'S                                                                    CHOICE ™                                                                   Methiocarb BIO ® Slug-                                                                 1/6   1/6   2/6 1/6 0/6 2/6 1/6 2/6  10/48                       Gard                                                                          Fe EDTA      2/6   4/6   2/6 2/6 4/6 2/6 2/6 0/6  18/48                       ______________________________________                                    

Summary

Examples 26 and 27 both show that a 9% Fe EDTA formulation is a far moreeffective molluscicide than any other brand used in the experiments.

In Examples 28 and 29, a comparison of various chelate compositions wascarried out.

Example 28

In this Example, the efficacies of Fe EDTA, ferric sodiumdiethylenetriaminetetraacetic acid (here referred to as D-Fe-11) andferrous sulphate+EDTA were compared to a control. The weather conditionswere cool and a high bran formulation was used. The dead snails werecollected and counted after 8 days. The results are shown in Table 28.

                  TABLE 28                                                        ______________________________________                                        Comparison of the efficacies of Fe EDTA, D-Fe-11 and FeSO.sub.4 +             Na.sub.2 EDTA.                                                                ______________________________________                                        Control     0/6    0/6    0/6  0/6  0/6  0/6  0/36                            D-Fe-11     0/6    1/6    1/6  0/6  0/6  0/6  2/36                            FeSO.sub.4 * + Na.sub.2 EDTA                                                              0/6    0/6    0/6  0/6  0/6  0/6  0/36                            Fe EDTA     3/6    3/6    1/6  0/6  0/6  1/6  8/36                            ______________________________________                                         *same Fe conc as in Fe EDTA ratio of FeSO.sub.4 :Na.sub.2 EDTA to give        ferrous disodium EDTA.                                                        DFe-11 is ferric sodium diethylenetriaminepentaacetic acid.              

Example 29

In this Example, the efficacies of Fe EDTA, ferric sodiumethylenediamine bis[(2-hydroxyphenyl)acetic acid] (here referred to asQ-Fe-6) (Akzo Chemicals) and ferrous sulphate +NtaEDTA were compared.The same conditions as in Example 28 were employed. The results areshown in Table 29.

                  TABLE 29                                                        ______________________________________                                        Comparison of the efficacies of Fe EDTA, Q--Fe-6 and                          FeSO.sub.4 + Na.sub.2 EDTA.                                                   ______________________________________                                        Control      0/6     0/6   0/6   0/6 0/6   0/30                               Q--Fe-6      1/6     2/6   0/6   0/6 1/6   4/30                               FeSO.sub.4 + Na.sub.2 EDTA                                                                 0/6     0/6   0/6   0/6 0/6   0/30                               Fe EDTA      2/6     3/6   4/6   3/6 2/6   14/30                              ______________________________________                                    

Summary

The results from Examples 28 and 29 suggest that the composition ofFeSO₄ +Na₂ EDTA was totally ineffective as a molluscicide. Aninvestigation carried out on this composition revealed that it had avery low pH and the likely explanation for its ineffectiveness is thatit is unattractive to molluscs. These Examples also illustrate thataltering the chelating ligand results in a more effective molluscicidethan the FeSO₄ +Na₂ EDTA composition, but a less effective molluscicidethan Fe EDTA.

The results of the above two Examples led to the investigationillustrated in Examples 30 to 32 of the dependence of the efficacy onpH. These investigations utilized various aluminum and Fe(II) chelateformulations, compared with the Fe(III) EDTA formulation. Variousconcentrations of K₂ CO₃ were added to adjust the pH of the compositionstrialed.

The various formulations used were as follows:

Formulations A to E were made up from FeSO₄ +NA₂ EDTA+K₂ CO₃

    ______________________________________                                        Formulation A                                                                           0.65% Fe as Fe(II)EDTA + 4.8% K.sub.2 CO.sub.3 pH = 9.5             Formulation B                                                                           0.65% Fe as Fe(II)EDTA + 2.0% K.sub.2 CO.sub.3 pH = 7.8             Formulation C                                                                           0.55% Fe as Fe(II)EDTA + 1.0% K.sub.2 CO.sub.3 pH = 6.8             Formulation D                                                                           0.70% Fe as Fe(II)EDTA + 2.0% K.sub.2 CO.sub.3 pH = 6.8             Formulation E                                                                           1.80% Fe as Fe(II)EDTA + 4.5% K.sub.2 CO.sub.3 pH                   ______________________________________                                                  = 7                                                             

Formulations F to J were all aluminum chelate formulations.

    ______________________________________                                        Formulation F                                                                          1.1% Al as aluminium potassium salt of EDTA                          Formulation G                                                                          0.55% Al as aluminium potassium salt of trans-1,2-                            diaminocyclohexane-N,N,N',N'-tetraacetic acid                        Formulation H                                                                          0.61% Al as aluminium potassium salt of 1,6-diamino-                          hexane-N,N,N',N'-tetraacetic acid                                    Formulation I                                                                          1.1% Al as aluminium potassium salt of 1,3-diamino-2-                         hydroxypropane-N,N,N',N'-tetraacetic acid                            Formulation J                                                                          1.2% Al as aluminium potassium salt of 1,2-diamino-                           propane-N,N,N',N'-tetraacetic acid                                   ______________________________________                                    

Example 30

In this Example, the variety of snail used was Helix aspersa within atemperature range of 18-29° C., using a high bran formulation. The deadsnails were removed and counted after 7 days. The results are shown inTable 30.

                  TABLE 30                                                        ______________________________________                                        Comparison of the efficacies of various aluminium and                         iron chelate formulations.                                                    ______________________________________                                        Control  0/3   0/3   0/3 0/3  0/3  0/3  0/3  0/3   0/24                       Formulation A                                                                          3/3   3/3   3/3 3/3  2/3  3/3  2/3  3/3  22/24                       Formulation B                                                                          0/3   3/3   1/3 0/3  1/3  2/3  3/3  3/3  13/24                       Formulation C                                                                          1/3   2/3   3/3 1/3  1/3  3/3  2/3  3/3  16/24                       Formulation D                                                                          1/3   3/3   3/3 3/3  3/3  3/3  3/3  1/3  20/24                       Formulation E                                                                          2/3   0/3   1/3 1/3  1/3  0/3  0/3  1/3   6/24                       Formulation F                                                                          0/3   0/3   1/3 0/3  1/3  3/3  0/3  1/3   6/24                       ______________________________________                                    

Example 31

In this Example, the variety of snail employed was Theba pisana . Thetrial was conducted within a temperature range of 18-23 ° C., using ahigh bran bait formulation. The dead snails were removed and countedafter 7 days. The results are shown in Table 31.

                  TABLE 31                                                        ______________________________________                                        Comparison of the efficacies of various aluminium and                         Fe EDTA formulations.                                                         ______________________________________                                        Control  0/6   0/6   2/6 0/6  0/6  0/6  0/6  0/6   2/48                       Formulation E                                                                          6/6   6/6   5/6 4/6  5/6  5/6  4/6  4/6  39/48                       Formulation F                                                                          2/6   1/6   2/6 2/6  2/6  0/6  2/6  2/6  13/48                       Formulation I                                                                          2/6   0/6   0/6 0/6  0/6  0/6  0/6  0/6   2/48                       Formulation J                                                                          1/6   1/6   0/6 1/6  0/6  2/6  2/6  0/6   7/48                       ______________________________________                                    

Example 32

In this Example, the conditions employed were the same as for Example31, except that the variety of snail employed was Helix aspersa. Thedead snails were removed and collected after 7 days. The results areshown in Table 32.

                  TABLE 32                                                        ______________________________________                                        Comparison of the efficacies of various aluminium and                         iron chelate formulations.                                                    ______________________________________                                        Control  0/6   0/6   0/6 0/6 0/6  0/6  0/6  0/6  0/48                         Formulation E                                                                          3/6   3/6   2/6 5/6 2/6  1/6  2/6  4/6  22/48                        Formulation F                                                                          1/6   0/6   0/6 1/6 0/6  0/6  0/6  0/6  2/48                         Formulation G                                                                          0/6   2/6   0/6 0/6 1/6  1/6  0/6  0/6  4/48                         Formulation H                                                                          1/6   0/6   0/6 0/6 0/6  0/6  0/6  0/6  1/48                         Formulation I                                                                          0/6   0/6   0/6 0/6 0/6  0/6  0/6  0/6  0/48                         Formulation J                                                                          1/6   0/6   0/6 1/6 0/6  2/6  1/6  0/6  5/48                         9% Fe EDTA                                                                             5/6   6/6   5/6 6/6 6/6  6/6  5/6  5/6  44/48                        ______________________________________                                    

Summary

The results from Examples 30 to 32 show that 9% ferric EDTA is the mosteffective composition of those chosen for trial. The aluminum chelateswere found to be not particularly effective, although of those trialed,the EDTA complex appears to have been the most successful.

Example 33

In this Example, the efficacies of various concentrations of ferrousEDTA were compared with 9% ferric EDTA (pH of about 7), Zeneca (a U. K.product containing 4% metaldehyde), PBI (a U. K. product containingapproximately 3% metaldehyde) and Pets'Choice 50% (based on a mustardseed by-product recently introduced onto the Australian market). Thesnail variety was Helix aspersa and the temperature range at which thetrial was conducted was 18-26° C. The results are shown in Table 33.

The various concentrations of Fe(II) EDTA had the following pH valuesand were adjusted with K₂ CO₃ :

8.9% Fe(II) EDTA pH=5.6

8.7% Fe(II) EDTA pH=5.7

8.6% Fe(II) EDTA pH=6.2

                  TABLE 33                                                        ______________________________________                                        Comparison of the efficacies of various concentrations of Fe(II) EDTA,        9% Fe(III) EDTA, Zeneca, PBI and Pets' Choice.                                ______________________________________                                        Control    0/6   0/6   0/6  0/6  1/6  0/6  0/6   1/36                         9% Fe(III) EDTA                                                                          3/6   3/6   4/6  3/6  4/6  2/6  4/6  20/36                         Zeneca     3/6   2/6   2/6  2/6  1/6  0/6  0/6  10/36                         PBI        0/6   2/6   0/6  1/6  1/6  0/6  1/6   5/36                         Pets' Choice 50%                                                                         3/6   4/6   3/6  2/6  4/6  1/6  1/6  18/36                         8.9% Fe(II) EDTA                                                                         5/6   4/6   1/6  1/6  1/6  1/6  1/6  14/36                         8.7% Fe(II) EDTA                                                                         6/6   2/6   3/6  6/6  4/6  0/6  0/6  21/36                         8.6% Fe(II) EDTA                                                                         4/6   5/6   1/6  3/6  2/6  2/6  2/6  19/36                         ______________________________________                                    

Summary

It can be seen from this study that 8.6% and 8.7% Fe(II) EDTA are justas effective as 9% Fe(III) EDTA and all the formulations containingchelates are more effective as a molluscicide than Zeneca or PBI.

Example 34

In this Example, the efficacies of baits containing variousconcentrations of K₂ CO₃ and Fe(III) EDTA were compared with that of 9%Fe(III) EDTA. The temperature range at which the trial was conducted was17-26° C. and the snail variety was Helix asperse. The results are shownin Table 34.

The pH's of the various formulations were as follows:

    ______________________________________                                        Formulation 1                                                                          40 g bran/flour + 0.00376 mole K.sub.2 CO.sub.3 + 3.5 g Fe EDTA               pH = 7.3 (8% Fe(OH)EDTA)                                             Formulation 2                                                                          40 g bran/flour + 0.00752 mole K.sub.2 CO.sub.3 + 3.5 g Fe EDTA               pH = 7.8 (8% Fe(OH)EDTA)                                             Formulation 3                                                                          40 g bran/flour + 0.01113 mole K.sub.2 CO.sub.3 + 3.32 g Fe                   EDTA pH = 10.0 (7.7% Fe(OH)EDTA)                                     Formulation 4                                                                          40 g bran/flour + 0.0151 mole K.sub.2 CO.sub.3 + 3.25 g Fe EDTA               pH = 10.33 (7.6% Fe(OH)EDTA)                                         ______________________________________                                    

                  TABLE 34                                                        ______________________________________                                        Comparison of the efficacies of baits containing various concentrations       of                                                                            K.sub.2 CO.sub.3 and Fe(III) EDTA with 9% Fe(III) EDTA.                       ______________________________________                                        Control  0/6   1/6   0/6 0/6 0/6  0/6  0/6  0/6   1/48                        9% Fe EDTA                                                                             5/6   6/6   4/6 4/6 6/6  3/6  4/6  5/6  37/48                        Formulation 1                                                                          6/6   5/6   4/6 4/6 4/6  2/6  3/6  4/6  28/48                        Formulation 2                                                                          2/6   3/6   1/6 2/6 3/6  3/6  6/6  4/6  24/48                        Formulation 3                                                                          6/6   3/6   2/6 2/6 0/6  3/6  2/6  2/6  20/48                        Formulation 4                                                                          2/6   3/6   2/6 2/6 2/6  2/6  5/6  4/6  22/48                        ______________________________________                                    

Example 35

In this Example, the efficacies of baits having various concentrationsof Al EDTA and different pH's were compared with baits having variousconcentrations of Fe EDTA. The temperature range at which the trial wasconducted was 17-20° C. and the snail variety was Helix aspersa. Theresults are shown in Table 35.

The pH's of the various formulations were as follows:

    ______________________________________                                        Formulation 5                                                                             20 g bran/flour + 0.1801 g Al EDTA pH = 9.37                                  (0.78% Al)                                                        Formulation 6                                                                             20 g bran/flour + 0.2390 g Al EDTA pH = 6.80                                  (1.04% Al)                                                        Formulation 7                                                                             20 g bran/flour + 0.2662 g Al EDTA pH = 8.63                                  (1.11% Al)                                                        Formulation 8                                                                             20 g bran/flour + 0.1405 g Al EDTA pH = 6.85                                  (0.62% Al)                                                        ______________________________________                                    

                  TABLE 35                                                        ______________________________________                                        Comparison of the efficacies of baits containing various concentrations       of Fe(III) EDTA and Al EDTA.                                                  ______________________________________                                        Control  0/3   0/3   1/3 1/3 1/3  0/3  2/3  0/3   5/24                        Formulation 1                                                                          2/3   1/1   1/1 2/3 1/1  1/1  1/1  2/3  11/14                        Formulation 2                                                                          3/3   2/3   2/3 1/3 2/3  2/3  2/3  1/3  15/24                        Formulation 3                                                                          2/3   2/3   2/3 3/3 2/3  2/3  2/3  2/3  17/24                        Formulation 5                                                                          3/3   3/3   3/3 2/3 1/2  2/3  2/3  3/3  19/23                        Formulation 6                                                                          3/3   2/3   2/3 2/3 2/3  2/2  1/2  2/3  16/22                        Formulation 7                                                                          1/3   2/3   2/3 2/3 2/3  3/3  2/3  2/3  16/24                        Formulation 8                                                                          3/3   3/3   3/3 3/3 2/3  1/2  2/3  3/3  20/23                        ______________________________________                                    

Summary

It appears from the results in Examples 34 and 35 that both theFe(III)Off EDTA and Al EDTA formulations are effective for Helixaspersa. Previously, when the pH of the Al EDTA had not been adjusted,resulting in a very acidic composition (pH less than 4), it did notappear to work. The efficacy is not very pH dependent for near neutraland mildly alkaline, but it is poor at low pH. The composition usingAl(OH)₃ and Na₂ EDTAH₂ with no CaCO₃ or K₂ CO₃ added as a filler has avery low pH and its efficacy is correspondingly low. As the amount of K₂CO₃ is increased, the pH is increased with a corresponding increase inefficacy. It appears that mixtures of FeSO₄ +Na₂ EDTA+K₂ CO₃,(particularly the composition of Formulation A i.e. 0.65% Fe asFe(II)EDTA+4.8% K₂ CO₃) offer an alternative stomach poison, theefficacy of which appears to be similar to that of ferric EDTA andcertainly superior to the incorporation of aluminum chelates.

Those skilled in the art will appreciate that the invention describedherein is susceptible to variations and modifications other than thosespecifically described. It is to be understood that the inventionincludes all such variations and modifications. The invention alsoincludes all of the steps, features, compositions and compounds referredto or indicated in this specification, individually or collectively, andany and all combinations of any two or more of said steps or features.

What is claimed is:
 1. A stomach-action molluscicide comprising themetal complexone [Fe(OH)EDTA]²⁻ and a carrier therefore, wherein themolluscicide gives a pH above about 7 when added to water.
 2. Astomach-action molluscicide according to claim 1, wherein the metalcomplexone comprises about 6% to about 12% by weight of themolluscicide.